This invention relates to a lithium tantalate vibrator of the flexural mode type for use as a time standard in electronic timepieces, and more particularly this invention relates to the electro-mechanical coupling factor and cutting-out angle of such a vibrator.
The primary object of this invention is to provide a lithium tantalate vibrator of the flexural mode type having high stability which is achieved by improving the electro-mechanical coupling factor thereof.
Another object of this invention besides the above improvement is to provide a lithium tantalate vibrator of the flexural mode type having high stability and also superior temperature characteristics by suitably selecting the cut-out angle thereof.
Presently, quartz crystals are used in general as the piezo-electric vibrators for electronic timepieces such as watches. The reason is that the quartz crystal forms a single crystal having a very small amount of impurity and high chemical stability. But it is disadvantageous for use as a vibrator for watches due to the relatively small electro-mechanical coupling factor of quartz crystal. In general, the electro-mechanical coupling factor "k" of the quartz crystal vibrators of flexural mode the in present use has been small, on the order of approximately 0.04, and the curve of the capacity-resonance frequency variation is a gently sloping one.